The invention relates to an apparatus for the automatic transverse guidance of a vehicle along a traffic lane. Apparatuses of this kind are used in road vehicles, for example, to keep the vehicle in a particular traffic lane on a multilane road.
An apparatus of this kind is described in German Patent document DE 43 32 836 C1 (having a corresponding U.S. Pat. No. 5,485,378, the specification of which is expressly incoporated by reference herein). This apparatus is continuously active during driving, assuming that it is ready for operation, and superimposes steering-angle adjustments which stabilize the transverse position upon the steering angle settings effected by the driver. On the one hand, the driver is thereby largely relieved of continual steering interventions and, on the other hand, he or she retains the possibility of intervening in the vehicle steering for larger steering maneuvers, e.g. while changing lane during overtaking or passing maneuvers. As feedback, the exertion of a steering torque by the apparatus on the steering wheel can be provided at the steering wheel with the sense of steering associated with the automatic steering intervention and familiar to the driver. In case there is no vehicle readiness, e.g. because the quality of the images supplied by a video camera recording the roadway is insufficient, the apparatus remains deactivated. In this patent document, it is furthermore explained that, in the case of steering regulation methods implemented in experimental vehicles, it is known for the driver to be able to switch between manual and automatic steering operation.
German Patent document DE 42 21 015 A1 (having an equivalent U.S. Pat. No. 5,245,422) discloses a system for automatic transverse vehicle guidance, the activation of which is linked to the activation of another system in the vehicle for holding the longitudinal speed of the vehicle constant, i.e. a so-called "cruise control". Here, the driver has the possibility either of activating only the cruise control, by means of a first control switch, or activating the cruise control and the automatic transverse vehicle guidance system jointly by actuating a second control switch. The automatic transverse vehicle guidance-system is deactivated as soon as the steering force measured by a driver steering sensor and exerted on the steering wheel by the driver exceeds a specifiable level. As soon as the latter condition is no longer met, the automatic transverse vehicle guidance system is re-activated automatically. The automatic transverse vehicle guidance system can furthermore be switched off by pushing the brake pedal down fully or by actuating a dedicated control switch. When the driver pushes the accelerator pedal down fully, the cruise control can be temporarily overridden, the automatic transverse vehicle guidance system remaining active.
The technical problem underlying the invention is to provide an apparatus for automatic transverse vehicle guidance of the type mentioned above which exhibits a comparatively high degree of convenience in terms of functioning and use.
The present invention solves this problem by providing an apparatus for the automatic transverse guidance of a vehicle along a traffic lane, which can be activated by an activating actuation of an operating element. The actual transverse-position value present at the activation instant serves as a desired transverse-position value for subsequent automatic transverse guidance operation.
This apparatus for automatic transverse guidance of a vehicle along a traffic lane comprises an operating element, actuable by the user, for activating the apparatus such that the actual transverse-position value present at the activation instant serves as a desired transverse-position value for subsequent automatic transverse guidance operation. While conventional transverse vehicle guidance systems generally attempt only to keep the vehicle within the boundaries of the traffic lane by maintaining a specified desired transverse position which is invariable, i.e. to prevent the boundaries of the traffic lane from being crossed, the present apparatus makes it possible for the vehicle user to specify any transverse vehicle position he or she wants as a desired transverse guidance position. For this purpose, he or she brings the vehicle into the corresponding desired transverse position, which can, in particular, be a position on the traffic lane which is further to the right or left, out of center, and then uses the operating element to activate the apparatus for automatic transverse vehicle guidance, which then keeps the vehicle in the desired transverse position.
An apparatus developed in accordance with a preferred embodiment is deactivated automatically when a steering intervention by the driver, which changes the transverse position, occurs. Thereafter, in a first alternative, the apparatus is not automatically re-activated or, in a second alternative, is automatically re-activated only when the monitored transverse vehicle dynamics exhibit a steady-state behavior for a specifiable waiting time, i.e. do not exceed certain tolerance limits as regards the transverse position or the lateral speed to the left and right during this waiting time. This offers safety advantages over the above-mentioned known automatic re-activation when the steering force exerted by the driver has become sufficiently small. This is because, in the case of overtaking maneuvers, there are often periods of time of greater or lesser length in which the driver does not have to exert any force on the steering wheel. Automatic re-activation of the previously deactivated automatic transverse guidance is undesirable at this moment. Moreover, the steering wheel is usually never completely free from forces during cornering, with the result that, in the case of the conventional procedure, re-activation of automatic transverse vehicle guidance can only take place on a sufficiently straight road section. In addition, transverse sloping of the traffic lane requires a small steering deflection, with the result that it is then unclear to the driver when the conventional transverse vehicle guidance system is re-activated after a traffic lane change. A further difficulty of this conventional system consists in that, after a prolonged period of driving with manual steering intervention, the driver may no longer be reckoning with re-activation of the system. All these problems do not occur with the apparatus according to the invention since their re-activation is not coupled to the steering force exerted by the driver and no longer occurs automatically, or occurs as a function of the time profile of the transverse vehicle dynamics.
A further advantageous apparatus offers a particularly high degree of convenience in terms of functioning and use by virtue of the fact that it comprises a multifunction operating element with two sets of two opposing directions of actuation in each case. The first set of opposing directions of actuation serves for the manual activation and deactivation of the apparatus, while the second set of opposing directions of actuation serves for the continuous changing of the desired transverse-position value to the left or right. The last-mentioned function makes it possible for the vehicle user to make continuous changes, as desired, to the desired transverse-position value, which is set to the actual transverse-position value at the instant of activation of the apparatus for automatic transverse guidance. To this end, there is no need for the driver first of all to deactivate the apparatus again and move the vehicle to the corresponding transverse position.
In the case of another advantageous apparatus, the multifunction operating element is configured as an operating lever which, along a first line of actuation, activates the apparatus upon being pulled and deactivates it upon being pushed. Along a second line of actuation, preferably orthogonal to the first, the multifunctional operating element changes the desired transverse-position value to the right by actuation in one direction and changes it to the left by actuation in the other direction.
An advantageous apparatus contains one or more indication elements, each of which indicates to the driver whether the apparatus is ready, i.e. is fundamentally prepared to carry out automatic transverse vehicle guidance and/or whether it is active at that moment. These indications can be given acoustically, optically and/or haptically.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.